Assuming the content that is being provided for printing is as it should be—that the design is effective, the images are high quality, that text has been proofed, and all pre-production bases have been covered—what do we need to know to obtain a high-quality printed piece? These questions and answers, provided by the Office of University Communications and Marketing, should help to enhance your understanding of the print production process.
What’s the difference between digital and offset printing?
There are many differences between digital and offset printing. Digital presses are basically high-end color copiers that use powder toner. Jobs are printed from art files sent directly from a computer. There is no ability to adjust color while the job is printing.
Offset printing uses large offset presses that print with liquid inks. In order to print offset, the art files are separated into the four process colors: black, yellow, magenta and cyan. The color separated art files are sent to a plate making machine that creates a printing plate for each color. The plates are hung on the printing units of the press. Paper passes through the press and the images are printed on the paper one color at a time. Offset printing allows for color adjustment throughout the printing process.
How do these two types of printing differ in terms of process, as well as quantity, quality, cost and turnaround time?
Digital printing is much faster than offset printing due to the fact that files are printed directly. Digital printing is most cost effective for smaller print projects such as postcards and Brochures up to a quantity of 1,000. The quality of digital printing is good, but color adjustments are not able to be made, so adjustments must be made to the original file.
Offset printing is more cost-effective for quantities over 1,000 and for larger projects such as large posters or signs and magazines. It takes longer to produce a job on an offset press. Proofs are not printed on the press; inkjet-printed high-resolution proofs are generated from the art files. These proofs represent, as close as possible, what the printed piece will look like. Color adjustments and other corrections can be noted on the proofs for the printer to fix, then a corrected second proof is shown for approval. When the proofs are approved, the plates are made, and the job is printed.
How do the processes differ in terms of the types of paper stocks that can be used?
Most printing papers are compatible for both digital and offset printing presses.
How do they differ in terms of environmental impact?
Most stocks are recyclable. There are a few cases where a coating may be applied to an offset printed sheet, such as a UV coating that makes the paper un-recyclable.
Offset Printing Quality Control
What should you be sure to look for at a press check?
Make sure that everything on the approved proof is on the printed sheet and that nothing is omitted, hidden or cropped off the press sheet. Make sure the inks are printing in register, that there are no halos around items, and that reverse type is clean and readable. Make sure the inks are strong and the color of the press sheet matches the color of the proof. Make any color adjustments that may be needed to make the press sheet match the approved proof.
Walk to the paper-feed end of the press and make sure the printer is using the stock that was selected for print and that substitutions were not made. Check the printer’s work order to make sure they have the correct specs (size, paper stock, etc.) and print quantity.
Discuss the delivery date and shipping information with the printer to ensure that the printer has the correct information.
What should you be sure to look for when reviewing a print proof?
Make sure everything that should be on the sheet is on the sheet, check the color of the images and have the designer make any needed color adjustments to the original file. Make sure the type is readable (not too small or hard to read on a photo).
What should you be sure to look for when reviewing a color or Epson proof?
Make sure everything that should be on the sheet is on the sheet. Check the color of the images and have the printer make any needed color adjustments to the original file. Make sure the type is readable (not too small or hard to read on a photo).
What do each of these anomalies look like on a proof (or on a printed piece if not corrected)?
Offsetting: This is when the wet inks of a freshly printed sheet rub off on the back of the sheet that’s on top. This results in a poor-quality print job. Offsetting today is rare since most printers use acqueous coating or UV inks, so the sheets come off the press dry.
Ghosting: This usually happens when printing a large, solid area of ink. The press can’t apply enough ink to cover the entire area evenly, so areas of weak, uneven ink application appear on the sheet.
Poor registration: This occurs when the dots of the four colors are not aligned on the sheet properly. When this happens, reverse type will not appear white, and photos and screen builds will appear fuzzy and out of focus.
Why is drying time important in offset printing? What things factor in to drying time?
The second side of a sheet cannot be printed until the first side is dry. If the first side is not dry, the press will mar the printing on the first side when the second side is printed. This could delay delivery of the job.
Several factors can affect the drying time of a sheet, including how much ink was printed, how much drying powder the printer used, the stock being used and the humidity in the press room. With the use of aqueous coating and UV inks, most jobs come off the press dry, and the second side can be printed immediately.
What are the different types of print binding and when should each be used?
The two most common types of binding are saddle stitching (staples) and perfect binding. Saddle stitching is mostly used for magazines and brochures. It’s the less expensive of the two binding types, and most printer have this capability in their shops.
Perfect binding—using glue to hold the pages together—is used for more formal print pieces such as event programs or catalogs. Perfect binding is also used when the page count is too high for saddle stitching.
Digital Printing Quality Control
Should I ask for a proof if I’m printing digitally?
A proof of a digital job is actually a printed sample of the job. A proof of a digital job must be seen to ensure that the file provided will print properly.
Should I expect my digital reprint to exactly match the original printed piece?
The printed piece should match the approved proof exactly because the proof is actually a digitally printed sample.
Does digital printing require drying time?
No. Digital presses use powered toners and not liquid inks, so there is no drying time.
Other Types of Printing
What is screen printing?
Screen printing has been replaced by large format digital printing.
What is engraving? When is it used?
Engraving is hand carving the art into a hard surface—usually copper—to create the printing plate. Because this cutting is done by hand, great detail can be cut into the plate. This method is used to print money, stock certificates, bonds, checks, and other security-sensitive papers. Due to the fine detail, the art is almost impossible to recreate making counterfeiting difficult.
Are there any other types of printing that could be commonly used when producing marketing collateral?
Web offset printing is another form of offset printing where the paper is fed into the press from large rolls of paper instead of individual sheets. These presses print fast, usually around 30,000 copies an hour, which makes them suitable for printing quantities greater than 100,000. Web printing is the same proofing process as that used for sheet-fed printing.